What is the largest number of human beings in space at the same time, and what vessels were they on when it happened?
The record appears to be 13. This has happened at least three times, once in 1995 and twice in 2009.
There are many other interesting records related to human spaceflight. On March 14, 1995, a record number of thirteen people were in space at one time. Seven of them were Americans that were on the STS 67 Endeavour, three cosmonauts were on the Mir space station, and an astronaut from the United States, along with two cosmonauts, were aboard Soyuz TM21.
Soyuz TMA-14: Three people aboard, including space tourist Charles Simonyi and the new Expedition 19 crew for the station which numbers two, a Russian and an American. Launched Thursday and will arrive at the station Saturday morning.
Space Shuttle Discovery: Seven people aboard, returning from the space station after delivering the last pair of U.S. solar wings to the orbiting laboratory, boosting it to full power during their STS-119 mission. The shuttle is due to land Saturday in Florida to end a 13-day spaceflight.
International Space Station: Currently home to three astronauts, one each from the United States, Russia and Japan. Two will return home April 7 with Simonyi to end their Expedition 18 mission.
The population boost came from the influx of seven newcomers aboard the space shuttle Endeavour, which docked Friday at 1:47 p.m. EDT (1747 GMT), and opened its hatch into the station a couple hours later.
"The crew of STS-127 is extremely happy to be here," replied Endeavour's STS-127 commander Mark Polansky. "Thirteen is a pretty big number but it's going to be an outstanding visit for us."
Polansky came with pilot Doug Hurley, and mission specialists Chris Cassidy, Julie Payette, Tom Marshburn, Tim Kopra and Dave Wolf. Waiting onboard the station with Padalka were Roman Romanenko, Michael Barratt, Robert Thirsk, Frank De Winne and Koichi Wakata.
On July 11th 2021 16 people were in space1 at the same time.
- Seven people on the International Space Station: Three Americans, two Russians, and one from both France and Japan.
- Three Chinese on the Tiangong Space Station.
- Six people on Virgin Galactic's Unity, including Richard Branson, two pilots, and three Virgin Galactic employees.
Note that SpaceX goes to orbit, whereas Virgin Galactic and Blue Origin currently do not. That's worth keeping in mind when considering these records.
1Unity reached a height of 88km, and any flight above 80km is considered space by NASA and the US military. The FAI, though, defines space as beginning at the Karman line 100km above the surface of the Earth.